U.S. patent number 8,155,227 [Application Number 13/160,872] was granted by the patent office on 2012-04-10 for mobile station apparatus, communication method, and base station apparatus.
This patent grant is currently assigned to Panasonic Corporation. Invention is credited to Jinsong Duan, Keisuke Ebiko, Atsushi Sumasu, Keiji Takakusaki, Mitsuru Uesugi.
United States Patent |
8,155,227 |
Duan , et al. |
April 10, 2012 |
**Please see images for:
( Certificate of Correction ) ** |
Mobile station apparatus, communication method, and base station
apparatus
Abstract
A mobile terminal device for performing multi-carrier
communication with a base station device can improve communication
quality while reducing the data amount without lowering accuracy of
feedback information. In the mobile station device (100), a
reception level measuring unit (135) measuring SINR as a reception
level for each chunk formed by a plurality of sub-carriers
according to a known signal; a control information transmission
control unit (160) transmits feedback information (CQI information)
based on the communication quality of each chunk to a base station
device (200); a relative value calculation unit (150) calculates a
relative value of MCS corresponding to the reception level between
adjacent chunks from the reception level of each chunk; and a CQI
information generation unit (155) generates feedback information
(CQI information) from an absolute value of MCS corresponding to
the reception level of the reference chunk and a relative value of
MCS corresponding to the reception level between the adjacent
chunks.
Inventors: |
Duan; Jinsong (Osaka,
JP), Uesugi; Mitsuru (Kanagawa, JP), Ebiko;
Keisuke (Osaka, JP), Takakusaki; Keiji (Kanagawa,
JP), Sumasu; Atsushi (Osaka, JP) |
Assignee: |
Panasonic Corporation (Osaka,
JP)
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Family
ID: |
37708588 |
Appl.
No.: |
13/160,872 |
Filed: |
June 15, 2011 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20110243027 A1 |
Oct 6, 2011 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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11997710 |
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PCT/JP2005/014336 |
Aug 4, 2005 |
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Current U.S.
Class: |
375/260; 375/299;
375/347; 375/349 |
Current CPC
Class: |
H04L
1/0029 (20130101); H04L 5/0091 (20130101); H04L
1/003 (20130101); H04L 1/0026 (20130101); H04L
5/0046 (20130101); H04L 5/006 (20130101); H04L
1/0009 (20130101); H04L 25/022 (20130101); H04L
5/0007 (20130101); H04L 1/0003 (20130101) |
Current International
Class: |
H04K
1/10 (20060101) |
Field of
Search: |
;375/260,299,347,349 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2003-169063 |
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Jun 2003 |
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JP |
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2004-104293 |
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Apr 2004 |
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JP |
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2004-208234 |
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Jul 2004 |
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JP |
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2004-532586 |
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Oct 2004 |
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JP |
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2005-159577 |
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Jun 2005 |
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JP |
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02/093757 |
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Nov 2002 |
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WO |
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2004/028065 |
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Apr 2004 |
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WO |
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2004/030263 |
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Apr 2004 |
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WO |
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2004/073245 |
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Aug 2004 |
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WO |
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Other References
International Search Report dated Nov. 15, 2005. cited by other
.
T. Baba, et al., "OFDM Tekio Hencho System ni Oite Career Hole
Siegyo o Michita Block Seigyogata Multi-level Soshin Denryoku
Siegyo Hoshiki ni Kansuru Kento," IEICE Technical Report, vol. 103,
No. 553, Jan. 9, 2004, pp. 11-16. cited by other .
J. Tomoto, et al., "Tekio Hencho o Mochiita Burst Mode OFDM Tsushin
Hoshiki ni Kansuru Kento," IEICE Technical Report, vol. 101, No.
280, Aug. 31, 2001, pp. 51-57. cited by other .
3GPP TSG RAN WG1 Ad Hoc on LTE, "Physical Channels and Multiplexing
in Evolved UTRA Downlink," Jun. 20-21, 2005, pp. 1-24. cited by
other .
Notice of the Reasons for Rejection dated Jun. 15, 2010. cited by
other .
Notice of Reasons for Rejection dated Sep. 14, 2010. cited by other
.
Japanese Office Action dated May 31, 2011. cited by other.
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Primary Examiner: Timory; Kabir A
Attorney, Agent or Firm: Dickinson Wright PLLC
Parent Case Text
This is a continuation application of application Ser. No.
11/997,710 which has a 371(c) date of Feb. 5, 2009 and which is a
national stage of PCT/JP2005/014336 filed Aug. 4, 2005, the entire
contents of each which are incorporated by reference herein.
Claims
The invention claimed is:
1. A base station apparatus comprising: a transmitting unit
configured to transmit, to a mobile station, data using groups,
into which subcarriers that are consecutive in a frequency domain
are divided in a predetermined unit of a time domain, and a
receiving unit configured to receive feedback information generated
based on a channel quality indicator (CQI) value, which is
calculated in the mobile station, and a differential value for each
of the groups, which is calculated in the mobile station, the CQI
value representing channel quality according to a first step size,
by which a range of the COI value is divided, the differential
value being a difference of the calculated CQI value with respect
to a single CQI value, which represents channel quality for all of
the groups, and being transformed according to a second step size,
which includes a step size greater than the first step size and by
which a range of the difference is divided, wherein: the feedback
information forms a data sequence, in which the single CQI value is
positioned at the beginning and the differential values for the
groups are positioned after the single CQI value in order of
increasing frequency or decreasing frequency.
2. The base station apparatus according to claim 1, wherein the
single CQI value which represents the channel quality for all of
the groups is an absolute value.
3. The base station apparatus according to claim 1, further
comprising a scheduling unit configured to schedule the data in
response to the received feedback information.
4. The base station apparatus according to claim 3, wherein said
scheduling unit determines a modulation and coding scheme (MCS) for
the data in response to the received feedback information.
5. The base station apparatus according to claim 1, wherein the CQI
value indicates a modulation and coding scheme (MCS).
6. A communication method comprising: transmitting, to a mobile
station, data using groups, into which subcarriers that are
consecutive in a frequency domain are divided in a predetermined
unit of a time domain, and receiving feedback info nation generated
based on a CQI value, which is calculated in the mobile station,
and a differential value for each of the groups, which is
calculated in the mobile station, the CQI value representing
channel quality according to a first step size, by which a range of
the CQI value is divided, the differential value being a difference
of the calculated CQI value with respect to a single CQI value,
which represents channel quality for all of the groups, and being
transformed according to a second step size, which includes a step
size greater than the first step size and by which a range of the
difference is divided, wherein: the feedback information forms a
data sequence, in which the single CQI value is positioned at the
beginning and the differential values for the groups are positioned
after the single CQI value in order of increasing frequency or
decreasing frequency.
Description
TECHNICAL FIELD
The present invention relates to a mobile station apparatus. More
particularly, the present invention relates to a mobile station
apparatus that performs multicarrier communication with a base
station apparatus.
BACKGROUND ART
In OFDM transmission, there are cases where communication quality
varies between subcarriers due to the influence of frequency
selective fading (see FIG. 1). Further, in downlink OFDM
transmission, channel states differ between terminals (UE), and so,
by making the UEs report communication quality, a base station
(Node-B) can select only subcarriers having good communication
quality and allocate transmission data per UE. This allocation
method is referred to as "frequency scheduling."
Generally, in order to perform frequency scheduling, it is
necessary for the terminals to measure received quality based on a
known pilot signal transmitted from the base station and report
communication quality information (CQI) based on the measurement
result to the base station. However, when the number of subcarriers
forming an OFDM signal is large and CQI is reported for all
subcarriers, the amount of CQI reporting becomes enormous, and a
problem arises that uplink radio resources are wasted.
Therefore, conventionally, various schemes for reducing the amount
of CQI reporting have been devised. For example, Non-Patent
Document 1 discloses using a relative value of received quality in
the time and frequency domain as shown in FIG. 1 and reducing the
amount of CQI reporting. To be more specific, as shown in FIG. 2,
for chunk #1, an absolute CQI value is reported. For other chunks,
relative values with respect to the CQI for chunk #1 (CQI relative
values) are reported. By this means, it is possible to reduce the
amount of data transmission for reporting, compared to the case of
reporting absolute CQI values for all chunks. Here, "chunk"
generally refers to a bundle of subcarriers consecutive in the
frequency domain. Particularly, in scheduling at the base station
apparatus, "chunk" refers to a two-dimensional (time domain and
frequency domain) bundle including a predetermined number of
subcarriers and a predetermined number of TTIs, and refers to a
minimum unit allocated to one terminal apparatus. Non-Patent
Document 1: NTT DOCOMO 3GPP R1-050590
DISCLOSURE OF INVENTION
Problems to be Solved by the Invention
In conventional OFDM transmission, there is the following problem.
That is, primarily, CQI relative values are always calculated using
CQI of one chunk at an edge in the frequency domain as a reference,
and therefore, under a circumstance where the number of bits
prepared for reporting CQI relative values is limited, frequency
selective fading patterns of substantial fluctuations cannot be
accurately represented. For example, as shown in FIG. 3, when CQI
relative values are reported using chunk 1 as a reference and the
number of bits prepared for showing CQI relative values is two, the
CQI relative values for chunk 5 and chunk 6 having CQI greatly
different from the CQI for chunk 1, cannot be shown with the
prepared bits. That is, when the selection of a chunk is not
appropriate for the reason that the chunk selected as a reference
is greatly different from the CQI for other chunks, the accuracy of
the CQI for other chunks deteriorates. Therefore, a problem arises
that communication quality deteriorates due to deterioration of the
accuracy of CQI reported values.
It is therefore an object of the present invention to provide a
mobile station apparatus that performs multicarrier communication
with a base station apparatus, and that makes it possible to reduce
the data amount for feedback and improve communication quality
without deteriorating the accuracy of feedback information.
Means for Solving the Problem
The mobile station apparatus of the present invention performs
multicarrier communication with a base station apparatus and adopts
a configuration including: a communication quality measuring
section that measures communication quality of each chunk comprised
of a plurality of subcarriers, based on a known signal; a
transmitting section that transmits feedback information based on
the communication quality of each chunk to the base station
apparatus; a relative value calculating section that calculates a
relative value of communication quality for adjacent chunks from
the communication quality of each chunk; and a feedback information
generating section that generates the feedback information from the
absolute value of the reference chunk and the absolute value of the
communication quality for the adjacent chunks.
Advantageous Effect of the Invention
According to the present invention, it is possible to provide a
mobile station apparatus that performs multicarrier communication
with a base station apparatus, and that makes it possible to reduce
the data amount for feedback and improve communication quality
without deteriorating the accuracy of feedback information.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 illustrates a state where communication quality of
subcarriers fluctuates due to the influence of frequency selective
fading;
FIG. 2 illustrates a method for generating feedback information of
a conventional mobile station apparatus;
FIG. 3 illustrates a method for generating feedback information of
the conventional mobile station apparatus;
FIG. 4 is a block diagram showing a configuration of a mobile
station apparatus according to Embodiment 1 of the present
invention;
FIG. 5 illustrates a method for generating feedback information of
the mobile station apparatus in FIG. 4;
FIG. 6 illustrates a method for generating feedback information of
the mobile station apparatus in FIG. 4;
FIG. 7 illustrates a method for generating feedback information of
the mobile station apparatus in FIG. 4;
FIG. 8 is a block diagram showing a configuration of a base station
apparatus according to Embodiment 1;
FIG. 9 illustrates another method for generating feedback
information of the mobile station apparatus in FIG. 4;
FIG. 10 illustrates still another method for generating feedback
information of the mobile station apparatus in FIG. 4;
FIG. 11 illustrates a method for generating feedback information of
the mobile station apparatus in FIG. 4;
FIG. 12 is a block diagram showing a configuration of a mobile
station apparatus according to Embodiment 2;
FIG. 13 illustrates change of a step size of the mobile station
apparatus in FIG. 12;
FIG. 14 shows an example of a structure of CQI information
according to Embodiment 2;
FIG. 15 is a block diagram showing a configuration of a base
station apparatus according to Embodiment 2;
FIG. 16 is a block diagram showing a configuration of a mobile
station apparatus according to Embodiment 3;
FIG. 17 illustrates change of a step size of the mobile station
apparatus in FIG. 16; and
FIG. 18 is a block diagram showing a configuration of a base
station apparatus according to Embodiment 3.
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described in detail
below with reference to the accompanying drawings. In the
embodiments, the same components will be assigned the same
reference numerals, and description thereof will be omitted.
(Embodiment 1)
As shown in FIG. 4, mobile station 100 of Embodiment 1 has RF
receiving section 105, GI removing section 110, FFT section 115,
demodulating section 120, error correction decoding section 125,
demultiplexing section 130, received level measuring section 135,
reference chunk determining section 140, MCS determining section
145, relative value calculating section 150, CQI information
generating section 155, control information transmission
controlling section 160, error correction coding section 165,
modulating section 170, IFFT section 175, GI inserting section 180
and RF transmitting section 185.
RF receiving section 105 receives a signal transmitted from base
station apparatus 200 (described later) and performs RF processing
such as down-conversion.
GI removing section 110 removes guard intervals from the received
signal subjected to RF processing and outputs the result to FFT
section 115.
FFT section 115 receives as input from GI removing section 110 the
received signal from which the guard intervals are removed and
performs FFT processing on this input signal. FFT section 115
outputs the received signal subjected to FFT processing to received
level measuring section 135 and demodulating section 120.
Received level measuring section 135 measures a received level of
each chunk using a pilot signal included in the received signal
subjected to FFT processing. Here, "chunk" refers to a group of
subcarriers consecutive in the frequency domain, a group of
non-consecutive subcarriers, or a range that is formed with a
plurality of subcarriers and TTI and that is specified by time and
frequency. Chunk is used as a minimum unit of resources allocated
to one mobile station (UE).
Reference chunk determining section 140 determines a chunk
(reference chunk) for which the absolute value of the modulation
and coding scheme (MCS) is reported to base station apparatus 200
(described later) as CQI information, according to predetermined
principles based on the received signal level (for example, SINR)
measured at received level measuring section 135. Predetermined
principles include, for example, principles of using a
predetermined chunk as the reference chunk and principles of using
the chunk having the highest received signal level as the reference
chunk. In Embodiment 1, it is assumed that the chunk having the
highest received signal level is determined as the reference chunk.
By using the chunk having the highest received signal level as the
reference chunk, the chunk having the best channel quality is used
as the reference chunk, so that it is possible to increase the
accuracy of CQI information generated based on this reference
chunk. Particularly, a relative value is used as a difference
(relative value), and therefore, if the difference step width does
not match the fluctuation width of the channel, the accuracy of CQI
may decrease in accordance with the distance from the reference
chunk. Generally, when frequency scheduling is performed, resources
are allocated to chunks having good CQI, and information of the
chunks having good CQI is regarded as important. Therefore,
regarding CQI information, it is particularly preferable to
increase the accuracy of information of the chunks having good
channel quality. Further, by using the chunk having a high received
signal level as a reference, the most reliable value is used as the
reference, and therefore reliability of relative values of other
chunks calculated based on the received signal level of this
reference chunk increases.
MCS determining section 145 determines the MCS corresponding to the
received level measured at received level measuring section 135 per
chunk.
Relative value calculating section 150 calculates relative values
of MCS's for adjacent chunks based on the reference chunk
determined at reference chunk determining section 140 and the MCS
of each chunk determined at MCS determining section 145.
To be more specific, first, relative value calculating section 150
temporarily stores the absolute value of the MCS for the reference
chunk, and calculates and temporarily stores the relative values of
MCS's for adjacent chunks for other chunks.
As a method of calculating relative values of MCS's for adjacent
chunks, for example, as shown in FIG. 5, relative values of MCS's
are calculated by changing chunks used as the reference for
calculating relative values, sequentially toward the reference
chunk in the frequency domain. To describe the method in more
detail with reference to FIG. 6, chunk 5 having the highest
received signal level is determined as the reference chunk in this
figure. Therefore, relative values for chunks 1 to 4 having lower
frequencies than chunk 5 which is the reference chunk, are
sequentially calculated in such a manner that the relative value of
the MCS for chunk 4 (a negative value in this figure) is calculated
using chunk 5 as a reference, and the relative value of the MCS for
chunk 3 is calculated using chunk 4 as a reference. Further,
relative values for chunks 6 to 8 having higher frequencies than
chunk 5 which is the reference chunk, are sequentially calculated
in such a manner that the relative value of the MCS for chunk 6 is
calculated using chunk 5 as a reference, and the relative value of
the MCS for chunk 7 is calculated using chunk 6 as a reference.
CQI information generating section 155 generates CQI using the
relative values for the adjacent chunks calculated at relative
value calculating section 150, the absolute value of the MCS for
the reference chunk, and reference chunk information from reference
chunk determining section 140.
CQI information is generated as shown in FIG. 7. That is, CQI
information generating section 155 arranges the number of the
reference chunk and the absolute value of the MCS for the reference
chunk at the head of a data stream, and, after that, sequentially
arranges the calculated relative values of MCS's for adjacent
chunks in the frequency domain in one direction from a chunk at an
edge in the frequency domain, that is, from the chunk having the
highest frequency or the chunk having the lowest frequency, and
generates CQI information.
Control information transmission controlling section 160 controls
transmission of the CQI information generated at CQI information
generating section 155 to base station apparatus 200 (described
later).
The CQI information outputted from control information transmission
controlling section 160 is subjected to error correction coding at
error correction coding section 165, modulated at modulating
section 170, and subjected to IFFT at IFFT section 175, and
transmitted to base station apparatus 200 (described later) via RF
transmitting section 185 after guard intervals are inserted at GI
inserting section 180.
Demodulating section 120 receives as input the received signal
subjected to FFT processing, demodulates the signal according to
radio resource allocation information and outputs the demodulated
received signal to error correction decoding section 125.
Error correction decoding section 125 receives as input the
demodulated received signal, performs error correction decoding
according to the radio resource allocation information and outputs
the error-correction decoded signal to demultiplexing section
130.
Demultiplexing section 130 receives as input the error-correction
decoded signal, demultiplexes the signal into various information
such as received data, radio resource allocation information and
CQI information, and outputs the radio resource allocation
information to demodulating section 120 and error correction
decoding section 125.
As shown in FIG. 8, base station apparatus 200 of Embodiment 1 has
RF receiving section 205, GI removing section 210, FFT section 215,
demodulating section 220, error correction decoding section 225,
demultiplexing section 230, CQI information receiving section 235,
CQI information analyzing section 240, scheduling section 245,
control information transmission controlling section 250,
multiplexing section 255, transmission data generating section 260,
pilot generating section 265, error correction coding section 270,
modulating section 275, IFFT section 280, GI inserting section 285
and RF transmitting section 290.
RF receiving section 205 receives a signal transmitted from mobile
station apparatus 100 and performs RF processing such as
down-conversion.
GI removing section 210 removes guard intervals from the received
signal subjected to RF processing and outputs the result to FFT
section 215.
FFT section 215 receives from GI removing section 210 as input the
received signal from which the guard intervals are removed, and
performs FFT processing on this input signal. FFT section 215
outputs the received signal subjected to FFT processing to
demodulating section 220.
Demodulating section 220 receives as input the received signal
subjected to FFT processing, demodulates the signal according to
the radio resource allocation information, and outputs the
demodulated received signal to error correction decoding section
225.
Error correction decoding section 225 receives as input the
demodulated received signal, performs error correction decoding
according to the radio resource allocation information, and outputs
the error-correction decoded signal to demultiplexing section
230.
Demultiplexing section 230 receives as input the error-correction
decoded signal, demultiplexes the signal into various information
such as received data, radio resource allocation information and
CQI information, outputs the radio resource allocation information
to demodulating section 220 and error correction decoding section
225, and outputs the CQI information to CQI information receiving
section 235. The outputted CQI information is outputted to CQI
information analyzing section 240 via CQI information receiving
section 235.
CQI information has the structure described above, that is, the
structure where the number of the reference chunk and the absolute
value of the MCS for the reference chunk are arranged at the head
of a data stream, and after that, the calculated relative values of
MCS's for adjacent chunks are sequentially arranged in the
frequency domain in one direction toward the reference chunk from a
chunk at an edge in the frequency domain, that is, from the chunk
having the highest frequency or the chunk having the lowest
frequency. Therefore, CQI information analyzing section 240
calculates absolute values of MCS's for all chunks based on this
CQI information. The absolute values of MCS's for the chunks are
outputted to scheduling section 245.
Scheduling section 245 performs scheduling based on the absolute
values of MCS's for the chunks, and outputs the scheduling
information to control information transmission controlling section
250. The scheduling information is outputted to multiplexing
section 255 according to control of control information
transmission controlling section 250.
Multiplexing section 255 receives as input and multiplexes
transmission data from transmission data generating section 260,
the pilot signal from pilot generating section 265 and the
scheduling information from control information transmission
controlling section 250. The multiplexed signal is subjected to
error correction coding at error correction coding section 270,
modulated at modulating section 275, subjected to IFFT at IFFT
section 280, and transmitted to mobile station apparatus 100 via RF
transmitting section 290 after guard intervals are inserted at GI
inserting section 285.
In addition, a method has been described with the above description
where relative values of MCS's for adjacent chunks are calculated
by sequentially changing the reference from the reference chunk,
but this is by no means limiting, and it is also possible to
calculate relative values of MCS's in one direction from a chunk
having a lower frequency toward a chunk having a higher frequency
as shown in FIG. 9, or calculate relative values of MCS's in one
direction from a chunk having a higher frequency toward a chunk
having a lower frequency.
Further, a case has been described with the above description where
the MCS for each chunk is determined from the received signal level
measured at mobile station apparatus 100 and CQI information is
generated from the absolute value of the reference chunk and
relative values of MCS's for adjacent chunks. However, the present
invention is not limited to this, and it is also possible to use
the measured received signal level as CQI information without
determining MCS's at mobile station apparatus 100. That is, mobile
station apparatus 100 may generate CQI information using the
absolute value of the received signal level (for example, SINR) of
the reference chunk and relative values of the received signal
levels for adjacent chunks, and base station apparatus 200, which
is a CQI information receiving side, may determine MCS's using the
received CQI information and perform scheduling.
In this way, according to Embodiment 1, mobile station apparatus
100 that performs multicarrier communication with base station
apparatus 200, has: received signal level measuring section 135
that measures communication quality (for example, SINR as the
received level) of each chunk comprised of a plurality of
subcarriers based on a known signal (a pilot signal from base
station apparatus 200); control information transmission
controlling section 160 that transmits feedback information (CQI
information) based on the communication quality of each chunk to
base station apparatus 200; relative value calculating section 150
that calculates relative values of communication quality for
adjacent chunks (for example, relative values of SINR or relative
values of MCS corresponding to SINR) from the communication quality
of each chunk (for example, SINR as the received signal level); and
CQI information generating section 155 that generates feedback
information (CQI information) from the absolute value of the
reference chunk (for example, the absolute value of SINR, the
absolute value of an MCS corresponding to SINR) and the relative
values of communication quality for adjacent chunks (for example,
relative values of SINR or relative values of MCS's corresponding
to SINR).
By this means, feedback information is generated from the relative
values of communication quality for adjacent chunks, so that, for
example, even in a communication state where communication quality
substantially fluctuates as shown in FIG. 11, it is possible to
generate feedback information reflecting the fluctuation state of
communication quality without increasing the amount of information
for showing communication quality, reduce the data amount for
feedback and improve the accuracy of feedback information. As a
result, at base station apparatus 200 that receives feedback
information, scheduling and the like is performed based on accurate
feedback information, so that it is possible to improve
communication quality of mobile station apparatus 100 and base
station apparatus 200. Further, by using the relative values of
communication quality for adjacent chunks, it is possible to cover
a range of substantial change of CQI with the same number of bits
and represent communication quality in a range where communication
quality is greatly different from communication quality of the
reference chunk.
Further, mobile station apparatus 100 has reference chunk
determining section 140 that selects the chunk having the best
communication quality (for example, SINR as the received signal
level) as the reference chunk.
By this means, it is possible to select a chunk having the most
reliable communication quality. By transmitting feedback
information including the absolute value of communication quality
of this reference chunk to base station apparatus 200, the
reliability of absolute values of communication quality for each
chunk which are calculated by converting feedback information at
base station apparatus 200 increases, so that it is possible to
improve communication quality of mobile station apparatus 100 and
base station apparatus 200.
Further, mobile station apparatus 100 has MCS determining section
145 that determines an MCS for each chunk based on communication
quality of each chunk measured at received level measuring section
135. Relative value calculating section 150 calculates relative
values of MCS's for adjacent chunks, and CQI information generating
section 155 generates CQI information from the absolute value of
the MCS for the reference chunk and the relative values of MCS's
for adjacent chunks.
(Embodiment 2)
In embodiment 1, relative values of MCS's are always reported per
MCS. By contrast with this, in Embodiment 2, the report granularity
for reporting relative values of MCS's (step size) is changed
according to channel state between the base station apparatus
(Node-B) and the mobile station apparatus (UE).
As shown in FIG. 12, mobile station apparatus 300 of Embodiment 2
has step size determining section 310, relative value calculating
section 320 and CQI information generating section 330.
Step size determining section 310 estimates a channel state between
mobile station apparatus 300 and base station apparatus 400
(described later) based on the received signal level measured at
received level measuring section 135 and determines the report
granularity for reporting relative values of MCS's (step size)
according to this channel state. This step size information is
outputted to relative value calculating section 320.
Relative value calculating section 320 calculates CQI information
based on the step size information determined at step size
determining section 310, the reference chunk determined at
reference chunk determining section 140 and the MCS of each chunk
determined at MCS determining section 145.
To be more specific, first, relative value calculating section 320
temporarily stores the absolute value of the MCS for the reference
chunk and calculates and temporarily stores the relative values of
MCS's for adjacent chunks for other chunks. Relative value
calculating section 320 converts the calculated relative values of
MCS's for adjacent chunks based on the step size information. For
example, in FIG. 13, when the step size is 1 MCS, MCS 8 is the MCS
for the reference chunk, and MCS's for adjacent chunks are MCS 7
and MCS 6, relative values become 1 and 2, respectively. When the
step size is 2 MCS's, relative values become both 1, and the values
become converted relative values of MCS's for adjacent chunks. In
this way, by increasing the step size, even when the number of bits
used for showing relative values of MCS's is limited, it is
possible to follow substantial fluctuation of the relative
values.
CQI information generating section 330 generates CQI information
using the relative values of MCS's for adjacent chunks calculated
at relative value calculating section 320, the absolute value of
the MCS for the reference chunk, the reference chunk information
from reference chunk determining section 140 and the step size
information from step size determining section 310. To be more
specific, a data structure is such that the step size information
is included in the CQI information shown in FIG. 7 (refer to FIG.
14).
As shown in FIG. 15, base station apparatus 400 of Embodiment 2 has
CQI information analyzing section 410. The CQI information adopts
the structure described above, that is, the data structure (FIG.
14) where the step size information is included in the CQI
information shown in FIG. 7, and CQI information analyzing section
410 calculates absolute values of MCS's for all chunks based on
this CQI information. To be more specific, the converted relative
values are inversely converted to relative values before conversion
based on the step size information, and absolute values of MCS's
for all chunks are calculated from the relative values before
conversion and the absolute value of the MCS for the reference
chunk. The absolute value of the MCS for each chunk is outputted to
scheduling section 245.
In this way, according to Embodiment 2, mobile station apparatus
300 that performs multicarrier communication with base station
apparatus 400, has: received level measuring section 135 that
measures communication quality (for example, SINR as the received
level) of each chunk comprised of a plurality of subcarriers based
on a known signal (pilot signal from base station apparatus 400);
control information transmission controlling section 160 that
transmits feedback information (CQI information) based on
communication quality of each chunk to base station apparatus 400;
relative value calculating section 320 that calculates relative
values of communication quality for adjacent chunks (for example,
relative values of SINR or relative values of MCS's corresponding
to SINR) from the communication quality of each chunk (for example,
SINR as the received level); and CQI information generating section
330 that generates feedback information (CQI information) from the
absolute value of communication quality of the reference chunk (for
example, the absolute value of SINR and the absolute value of MCS
corresponding to SINR) and the relative values of communication
quality for the adjacent chunks (for example, relative values of
SINR or relative values of MCS's corresponding to SINR).
Further, mobile station apparatus 300 has step size determining
section 310 that determines a report granularity (step size) for
reporting the relative values of communication quality (for
example, relative values of SINR or relative values of MCS's
corresponding to SINR) based on the measured communication quality
(for example, SINR as the received level). Relative value
calculating section 320 calculates converted relative values
obtained by converting the relative values of communication quality
according to the report granularity for reporting, and CQI
information generating section 330 generates the feedback
information from the absolute value of communication quality of the
reference chunk (for example, the absolute value of SINR and the
absolute value of MCS corresponding to SINR), the converted
relative values (for example, converted relative values of SINR or
converted relative values of MCS corresponding to SINR) and the
report granularity for reporting.
By this means, the report granularity for reporting can be changed
adaptively according to communication quality, so that, even in a
communication state where communication quality fluctuates
substantially, it is possible to generate feedback information
accurately reflecting fluctuation state of communication quality
without increasing the amount of information for showing
communication quality, reduce the data amount for feedback and
improve the accuracy of feedback information. As a result, at base
station apparatus 400 that receives feedback information,
scheduling or the like can be performed based on accurate feedback
information, so that it is possible to improve communication
quality of mobile station apparatus 300 and base station apparatus
400.
(Embodiment 3)
In Embodiment 1, relative values of MCS's are always reported per
MCS. By contrast with this, in Embodiment 3, the report granularity
(step size) for reporting relative values of MCS's is determined
based on the MCS's determined from the received level of each chunk
of a pilot signal transmitted from the base station apparatus
(Node-B).
As shown in FIG. 16, mobile station apparatus 500 of Embodiment 3
has step size determining section 510, relative value calculating
section 520 and CQI information generating section 530.
Step size determining section 510 determines the report granularity
(step size) for reporting relative values of MCS's based on the MCS
of each chunk determined at MCS determining section 145.
To be more specific, as shown in. FIG. 17, step size determining
section 510 specifies the chunk having the maximum MCS and the
chunk having the minimum MCS from the MCS of each chunk determined
at MCS determining section 145. Mobile station apparatus 500
reports absolute values of the chunk having the maximum MCS and the
chunk having the minimum MCS to base station apparatus 600
(described later) as reference chunks. A difference between the
maximum chunk and the minimum chunk (range between the maximum MCS
and the minimum MCS) is divided into the number of ranges that can
be represented with the number of bits prepared for showing
correlation values of MCS's for adjacent chunks. The divided range
provides the step size in this embodiment. That is, step size
determining section 510 divides the range between the maximum MCS
and the minimum MCS into the number of ranges that can be
represented with the number of bits prepared for showing the
correlation values of MCS's for adjacent chunks to calculate the
step size. In this figure, the number of bits prepared for showing
the correlation values of MCS's for adjacent chunks is two, the
number of ranges that can be shown is four, the maximum minimum MCS
range is 8, and therefore the step size becomes 2 MCS's. Here,
although a case is described where the step sizes arc made uniform,
this is by no means limiting, and the range may be ununiformly
divided. Particularly, by increasing the number of divided ranges
for the range where the received level is high, that is, the MCS
level is high, and by decreasing the number of divided ranges for
the range where the received level is low, the range where the
reliability of the measured value of the received level is higher
can be represented accurately, so that it is possible to improve
the accuracy of CQI information.
Relative value calculating section 520 calculates CQI information
based on step size information determined at step size determining
section 510, the reference chunk determined at reference chunk
determining section 140 and the MCS of each chunk determined at MCS
determining section 145.
To be more specific, first, relative value calculating section 520
temporarily stores the absolute value of the MCS with respect to
the reference chunk, and calculates and temporarily stores relative
values of MCS's for adjacent chunks with respect to other chunks.
Relative value calculating section 520 converts the calculated
relative values of MCS's for adjacent chunks based on the step size
information.
CQI information generating section 530 generates CQI information
using the relative values of MCS's for adjacent chunks calculated
at relative value calculating section 520, the absolute value of
the MCS for the reference chunk, the reference chunk information
from reference chunk determining section 140 and the step size
information from step size determining section 510. To be more
specific, a data structure (FIG. 14) is such that step size
information is included in the CQI information shown in FIG. 7.
As shown in FIG. 18, base station apparatus 600 of Embodiment 3 has
CQI information analyzing section 610. The CQI information adopts
the structure as described above, that is, the data structure where
the step size information is included in the CQI information shown
in FIG. 7, and so CQI information analyzing section 610 calculates
absolute values of MCS's for all chunks based on this CQI
information. To be more specific, the converted relative values are
inversely converted to relative values before conversion based on
step size information, and the absolute values of MCS's for all
chunks are calculated from the relative values before conversion
and the absolute value of the MCS for the reference chunk. The
absolute value of the MCS for each chunk is outputted to scheduling
section 245.
In this way, according to Embodiment 3, mobile station apparatus
500 that performs multicarrier communication with base station
apparatus 600 has: received level measuring section 135 that
measures communication quality (for example, SINR as the received
level) of each chunk comprised of a plurality of subcarriers based
on a known signal (a pilot signal from base station apparatus 600);
control information transmission controlling section 160 that
transmits feedback information (CQI information) based on the
communication quality of each channel to base station apparatus
600; relative value calculating section 520 that calculates
relative values of communication quality for adjacent chunks (for
example, relative values of SINK or relative values of MCS's
corresponding to SINR) from communication quality of each chunk;
CQI information generating section 530 that generates feedback
information (CQI information) from the absolute value of
communication quality for the reference chunk (for example, the
absolute value of SINR or the absolute value of MCS corresponding
to SINR) and the relative values of communication quality for
adjacent chunks (for example, relative values of SINR or relative
values of MCS's corresponding to SINR).
Further, mobile station apparatus 500 has MCS determining section
145 that determines the MCS of each chunk based on measured
communication quality of each chunk (for example, SINR as the
received level); and step size determining section 510 that
determines the report granularity (step size) for reporting
relative values of communication quality (for example, relative
values of MCS corresponding to SINR) based on the width between the
maximum MCS and the minimum MCS out of MCS's determined at MCS
determining section 145 and the number of bits for showing relative
values of communication quality for adjacent chunks in feedback
information. Relative value calculating section 520 calculates
converted relative values obtained by converting the relative
values of communication quality according to the report granularity
for reporting, and CQI information generating section 530 generates
the feedback information from the absolute value of communication
quality for the reference chunk (for example, the absolute value of
MCS corresponding to SINR), the converted relative values (for
example, converted relative values of MCS's corresponding to SINR)
and the report granularity for reporting.
By this means, a report granularity for reporting can be adaptively
changed according to the communication quality, so that, even in a
communication state where communication quality fluctuates
substantially, it is possible to generate feedback information
accurately reflecting fluctuation state of communication quality
without increasing the amount of information for showing
communication quality, reduce the data amount for feedback and
improve the accuracy of feedback information. As a result, at base
station apparatus 600 that receives feedback information,
scheduling or the like can be performed based on accurate feedback
information, so that it is possible to improve communication
quality of mobile station apparatus 500 and base station apparatus
600.
(Other embodiments)
In Embodiments 1 to 3, a case has been described where the chunk
having the best communication quality is selected as the reference
chunk, but this is by no means limiting, and, for example, it is
also possible to determine a chunk having an MCS close to an
average value of MCS's for all chunks as a reference chunk.
Further, it is possible to select a reference chunk randomly or
select a reference chunk according to fixed patterns. Furthermore,
the base station may specify different patterns for reporting the
reference chunk to the mobile stations.
Industrial Applicability
The mobile station apparatus of the present invention performs
multicarrier communication such as OFDM communication with the base
station apparatus and is suitable for use as a mobile station
apparatus that reduces the data amount for feedback and improves
communication quality without decreasing the accuracy of feedback
information.
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